1. Field of the Invention
In internal combustion engines used in vehicles, a throttle device is currently used, which as a rule is in the form of a circular flap received in the intake system of the engine, and which meters the volumetric flow of fresh air to be aspirated that is required for the combustion. Because of the high flow velocities of the fresh-air flow, and at low outdoor temperatures, water vapor contained in the fresh air can condense on the wall of the pipe; upon further cooling, ice can form in the interior of the fresh-air line, which can impair the smooth operation of a throttle valve considerably.
2. Prior Art
German Patent Disclosure DE 33 46 167 A1 relates to a throttle valve connector in which a throttle valve is disposed on the shaft, which in turn is fixed on both ends in the connector housing by slide bearings. These slide bearings are each pressed into a shaft bore and have end faces, toward the throttle valve, which are curved to suit the wall of the housing bore and form a part of this wall. Because of this design of the slide bearings, the leakage rate of this throttle valve connector in DE 33 46 167 A1 is extremely slight.
German Patent Disclosure DE 198 43 771 A1 relates to an electric-motor final control element, in particular with a throttle valve. An electric-motor final control element is disclosed, with a housing and with an electric motor disposed on a drive side inside the housing for driving a movable element disposed in the housing. This movable element is in particular a throttle valve, and according to the disclosure it is provided that a separate electronic housing for receiving control and/or evaluation electronics can be secured to the housing. On the one hand, in particular this avoids the projection of electromagnetic interference to the inside, and on the other, mass-produced electronic final control elements that do not require any control unit can continue to be used without changes in shape being required for the production of the final control element.
Finally, from German Patent Disclosure DE 29 49 041 B1, a heater for mixture preparation in mixture formers has been disclosed. This version involves a heater for mixture preparation in internal combustion engine mixture formers, with a pipe wall that defines a main flow and with a main throttle member downstream, as well as a fuel distribution device in the upstream part of a mixing chamber. The latter is embodied, over a part of this length, as a double wall of a heat exchanger, with an annular hot water chamber that has a water inlet connector on one end and a water outlet connector on its other end. The heat exchanger communicates with a coolant loop via a thermally controlled ON valve that opens at elevated temperatures. When the ON valve is blocked, and when the coolant loop is turned off, the heat exchanger is located above the coolant level. The inner wall of the heat exchanger, adjoining the main flow path of the mixture former, comprises an electric heating resistor material and is electrically connected to a voltage source via an electrical switch member that is thermally controlled as a function of the coolant temperature and that opens beyond a certain, relatively high water temperature.
The advantages of the embodiment according to the present invention are considered to be above all that the conduits and hollow chambers, in which a heating medium flows, can already be fabricated in the process of producing the throttle device for an internal combustion engine, so that metal-cutting machining of the solid material comprising the throttle housing is unnecessary. If heating conduits on the throttle housing are produced later by being drilled open or milled from solid material, then the course of the heating conduits must necessarily match the geometry of the housing, which under some circumstances can mean that only uneven heating of the wall of the throttle plate bore is attainable, because some regions of the throttle housing, made of solid material, remain that have a relatively great wall thickness.
With the embodiment proposed according to the invention, the heating conduits are shaped during production in the region between the outer wall and the throttle valve bore in such a way that they allow the passage of a heating medium both parallel to the flow direction of the fresh-air flow andxe2x80x94if necessaryxe2x80x94perpendicular to the flow direction of a fluid flow flowing in the flow cross section. In an advantageous feature of the embodiment of the invention, the individual hollow chambers between the outer wall of the throttle device and the throttle valve bore can be joined together by lowering the ribs that subdivide the hollow chambers, so that by means of overflow processes at the wall of the throttle valve bore, a uniform temperature profile can develop. Upon assembly, the hollow chambers on the open side are sealed off, for instance by means of a continuous rib or by being mounted on a further component. If the throttle housing is produced in the form of cast parts, then in the casting the inlet and outlet connections necessary for connecting the heater can be positioned from outside relative to the hollow chambers in such a way that they define the surface of the throttle valve wall that is to be heated. The heating surface can be varied by placing the connections elsewhere.
With the arrangement of hollow chambers or heating conduits, made in accordance with the embodiment of the invention, between the outer wall of the throttle housing and the wall of the throttle valve bore, a uniformly proceeding temperature clamp or control, or tempering, of the wall of the throttle valve bore can be attained. Per hollow chamber segment, a tempering of the wall of the throttle valve bore can be accomplished that corresponds to the location of the inlet or outlet connections of the heating medium. The wall of the heating surfaces, that is, the boundary walls of the throttle valve bore, which are embodied with an extremely thin wall thickness, make a fast response time possible and thus a fast change of temperature at the wall of the throttle valve bore.